There could be a clause in the contract, or maybe Kathleen Kennedy doesn’t want to go against George’s wishes, or perhaps they just don’t care and would rather concentrate on making new movies. I don’t like any of the three excuses.
It’s a shame that such an important piece of history and culture was altered in the first place, but to not preserve the originals and give the public access to that very important part of cinema is proving they are poor custodians of the work and don’t appreciate its significance. I love their new movies, but please, respect where they came form.